Field of the Invention
The present invention relates to a solid state imaging device and an imaging system.
Description of the Related Art
In recent years, as a demand for quality of images has become higher, devices that correct offset voltages of output signals have been proposed. An image reading device disclosed in Japanese Patent Application Laid-open No. H11-027112 has a multi-chip linear sensor and each chip has a correction circuit of an offset voltage. A correction circuit on a selected chip outputs a reference voltage and correction circuits on non-selected chips correct the offset voltages based on the reference voltage. This intends to reduce offset voltage differences on output signals of respective chips.
In the device described above, when there is an offset voltage in a correction circuit on a non-selected chip, the offset voltage is not corrected and remains, which may cause degradation of an image. Further, when a differential operation between an output signal from each chip and a reference voltage is performed in a signal processing circuit outside the chip, a dynamic range may be limited in the signal processing circuit due to an offset voltage. For example, when there is a voltage difference between a reference voltage and an output signal when no light is irradiated on a chip, this may limit the maximum use of the range of an input voltage of the signal processing circuit.